Due to a rise in antisocial behaviour being caused by unaccompanied young people, branch bosses said children under 18 had been banned from the premises, unless under adult supervision.

Erin’s father, Mark Turnbull, 40, has been left angered by the new restrictions.

He said: “That’s only the second or third time Erin has been in town alone with her friend.

“They aren’t very confident yet, and one of the reasons you let your child go into town alone is to build their confidence gradually.

“Erin and Emma were both left upset by this, and I just wish I’d been there to witness it. I just couldn’t believe it.”

In July last year, we told how McDonald’s in Corstorphine was forced to hire bouncers for its doors after staff were repeatedly hassled by youths.

A spokeswoman for KFC said: “We are sorry to hear about Erin’s experience but the restaurant team have been dealing with antisocial behaviour relating to unaccompanied young people recently, which has led them to the restrictions.

“We are working with the police and local council on how to best manage this and, in the meantime, customers under 18 are welcome to visit our Princes Mall shopping centre restaurant just across the road.”

A spokesman for Police Scotland said: “We have a dedicated operation in place to tackle antisocial behaviour in the city centre.

“Operation Cerimon was set up to combat these issues at the east end of Princes Street. We are continuing to work closely with our partners, including Edinburgh City Council and local businesses.

“We are also working alongside a local youth cafe, called 6vt, to help engage with young people.”

A city council spokeswoman said: “We will continue to work closely with Police Scotland on all antisocial behaviour issues across the city to ensure that Edinburgh remains a safe place for its residents and visitors.”